Glass State Research Articles

Observation of Topological Hall Effect in a Chemically Complex Alloy.

The topological Hall effect (THE) is the transport response of chiral spin textures and thus can serve as a powerful probe for detecting and understanding these unconventional magnetic orders. So far, the THE is only observed in either noncentrosymmetric systems where spin chirality is stabilized by Dzyaloshinskii-Moriya interactions, or triangular-lattice magnets with Ruderman-Kittel-Kasuya-Yosida-type interactions. Here, a pronounced THE is observed in a Fe-Co-Ni-Mn chemically complex alloy with a simple face-centered cubic (fcc) structure across a wide range of temperatures and magnetic fields. The alloy is shown to have a strong magnetic frustration owing to the random occupation of magnetic atoms on the close-packed fcc lattice and the direct Heisenberg exchange interaction among atoms, as evidenced by the appearance of a reentrant spin glass state in the low-temperature regime and the first principles calculations. Consequently, THE is attributed to the nonvanishing spin chirality created by strong spin frustration under the external magnetic field, which is distinct from the mechanism responsible for the skyrmion systems, as well as geometrically frustrated magnets.

The influence of the Cr2O3–Mn2O3 colorants system on the spectral characteristics of R2O–PbO–SiO2 glasses

AbstractThe focus of this paper centers on an exploration of optical glasses with high transmittance within the infrared spectrum at wavelength of 1 060 nm, while concurrently demonstrating full absorption within the ultraviolet and visible spectral ranges. The paper analyzes the present state of glasses demonstrating necessary transmittance at IR range, considering their inherent strengths and limitations. In this context, an R2O–PbO–SiO2 glass system with Cr2O3–Mn2O3 colorants system emerges as the subject of this research. Research was conducted to comprehensively assess the impact of this colorant system on the glass spectral characteristics, while considering the potentially detrimental influence of FeO.The principles underlying the industrial production of these glasses are systematically elucidated and presented. It was discovered that using gas heating during the cooling phase of glass melting resulted in the disruption of the spectral homogeneity of the glass, ultimately leading to defective product outcomes. Implementing the methodology of gasless temperature reduction (inertial cooling process) before glass pouring has created a favorable environment for producing high‐quality items. Glass samples from the laboratory tests were obtained, and the researched glass was integrated into serial production.

Spin glass state in Co doped NdMnO3

The temperature-dependent ac susceptibility studies of in-phase component (χ′ac) and out of phase component (χac″) was done on a single phase polycrystalline NdMn0.6Co0.4O3 sample. The measurements were conducted in 4 Oe ac field and 0 Oe dc field at frequencies of 111, 311, 1011, and 1311 Hz. As the frequency increases, the magnitude of χ′ac decreases, and its peak position, corresponding to Tf, moves towards higher temperatures. This strongly suggests the presence of a spin glass (SG) state and the absence of long-range ferromagnetic ordering. The value of relative shift in freezing temperature (δTf) is found to be δTf = 0.0089, which suggests the existence of canonical SG state in NdMn0.6Co0.4O3 sample. To confirm it the ac susceptibility data was further analyzed using Arrhenius, Vogel Fulcher, and Power–law.

Magnetic field-induced narrow first-order and metamagnetic phase transitions of Nd5Ge3

We report on the magnetic behaviour of Nd5Ge3 by investigating through magnetization, neutron diffraction and muon spin relaxation measurements. Temperature dependent-magnetization, muon depolarization rate (λ), initial asymmetry (A0) and the stretched exponent (β) show a clear anomaly at the Néel temperature TN ∼ 54 K. However, the short-range correlated ferromagnetic interactions below TN are inferred from the diffuse scattering mechanism as revealed by zero-field neutron diffraction data. Narrow first order phase transition is due to the competing interaction of a high temperature weak-antiferromagnetic and low temperature glassy states. Magnetic field-induced reentrant spin glass state from a magnetic glass state is observed, before it transforms to a ferromagnetic state.

Thermal transformation arrest austenite in Ni-Co-Mn-In alloys within the martensite/strain-glass phase boundary

Thermal transformation arrest austenite is a remarkable phenomenon observed in alloys in which the martensitic transition is suppressed during the field cooling process, and austenite is reserved at low temperatures upon subsequent withdrawing magnetic field. Recent studies showed that thermal transformation arrest austenite is a special frozen state of strain glass, which only occurs in the martensitic/strain-glass phase boundary composition with a two-step transition. However, this phenomenon has just been verified in the Ni-Co-Mn-Sn system, and whether it is equally effective for other systems needs to be detected. To verify this viewpoint, the phase transforming properties of Ni45Co5Mn50-xInx (x = 13.3∼13.75) alloys are explored. We found that Ni45Co5Mn36.5In13.5 undergoes a two-step transition and exhibits thermal transformation arrest austenite behavior. Our experimental results show that thermal transformation arrest austenite is exclusively observed within the phase boundary in Ni45Co5Mn50-xInx system and provide valuable insights into the peculiar transformation behaviors in this system.

Scaling regimes and fluctuations of observables in computer glasses approaching the unjamming transition.

Under decompression, disordered solids undergo an unjamming transition where they become under-coordinated and lose their structural rigidity. The mechanical and vibrational properties of these materials have been an object of theoretical, numerical, and experimental research for decades. In the study of low-coordination solids, understanding the behavior and physical interpretation of observables that diverge near the transition is of particular importance. Several such quantities are length scales (ξ or l) that characterize the size of excitations, the decay of spatial correlations, the response to perturbations, or the effect of physical constraints in the boundary or bulk of the material. Additionally, the spatial and sample-to-sample fluctuations of macroscopic observables such as contact statistics or elastic moduli diverge approaching unjamming. Here, we discuss important connections between all of these quantities and present numerical results that characterize the scaling properties of sample-to-sample contact and shear modulus fluctuations in ensembles of low-coordination disordered sphere packings and spring networks. Overall, we highlight three distinct scaling regimes and two crossovers in the disorder quantifiers χz and χμ as functions of system size N and proximity to unjamming δz. As we discuss, χX relates to the standard deviation σX of the sample-to-sample distribution of the quantity X (e.g., excess coordination δz or shear modulus μ) for an ensemble of systems. Importantly, χμ has been linked to experimentally accessible quantities that pertain to sound attenuation and the density of vibrational states in glasses. We investigate similarities and differences in the behaviors of χz and χμ near the transition and discuss the implications of our findings on current literature, unifying findings in previous studies.

Crystallization of an undercooled Zn-based glass forming alloy

Zn-based metallic glasses (Zn40Mg11Ca31+xYb18-x, x = 0 - 4) are strong glass forming alloys with low glass transition temperatures. While the crystallization onset temperature is also low, the nucleation behavior has not been examined and analyzed quantitatively. For a Zn40Mg11Ca31Yb18 metallic glass alloy, the crystallization behavior was determined based on the application of the Flash differential scanning calorimetry (DSC) with ultrafast heating and cooling rates. The critical cooling rate range was measured for glass formation at 1.6(±0.2) × 104K/s. A temperature-time-transformation (TTT) diagram for the nucleation onset in an undercooled liquid was obtained by applying a series of isothermal exposures by fast heating from the glass state or fast cooling from the liquid state to the target temperatures. A heterogeneous nucleation analysis model was developed to interpret the experimental TTT diagram, which provided a further understanding of the nucleation in Zn-based metallic glasses.

Effects of gamma-irradiation on the superconducting properties of FeTe0.55Se0.45 single crystals grown by self-flux method

We have investigated the effect of gamma (γ)-irradiation on the structural and superconducting properties of FeTe0.55Se0.45 single crystals grown by the self-flux method. The impact of γ-irradiation on the superconducting transition temperature (TC), critical current density (JC), and vortex pinning mechanism has been systematically studied. The x-ray diffraction study reveals the growth of single crystals along the c-axis. The superconductivity has been confirmed in pristine and γ-irradiated samples through temperature-dependent resistivity (ρ(T)) and magnetization [M(T)] measurements. After irradiation, a slight improvement is observed in the upper critical field Hc2(0) values. The values of thermally activated energy have been calculated and a crossover from a single to collective vortex pinning regime is observed. Additionally, we have analyzed the vortex phase diagrams, revealing a transition from vortex liquid to vortex glass state. Furthermore, the presence of second magnetization peak (SMP) or fishtail effect has been noticed in the M(H) loops, and with increasing temperature, the position of SMP (Hsp) shifts toward lower magnetic field regions. The critical current density has been estimated by Bean's critical state model at different magnetic fields [JC(H)] and temperatures [JC(T)]. The defects through gamma-irradiation lead to a significant threefold increase in JC compared to pristine samples in self-field and at 2 K. The pinning mechanisms have been explained using collective pinning theory and the Dew-Hughes model by analyzing the normalized pinning force density. Our analysis indicates that δl-pinning is dominant and point defects are present in all the samples.

The trade-off anionic modulation in metal-organic glasses showing color-tunable persistent luminescence.

Ultralong room-temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF) materials provide exciting opportunities for the rational design of persistent luminescence owing to their long-lived excitons. However, conventional rare-earth-based all-inorganic emitters involve high cost and harsh synthesis conditions, and purely organic systems may require complicated synthesis routes and tedious purification. Therefore, it is highly desirable to develop a cost-effective and easily manufacturable method for achieving color-tunable RTP-TADF with a long afterglow. Herein, we demonstrate a rational strategy to introduce different anions (Cl-, Br- and OAc- ions) into a Zn-based metal-organic scaffold, which can improve the crystal rigidity and achieve a well-balanced RTP-TADF. Both theoretical and experimental studies have demonstrated that the adjustment of different anions can effectively modulate the spin-orbit coupling (SOC) and the energy gap of singlet-triplet states (ΔEST) and then tailor the afterglow lifetime. Moreover, we prepared dye-doped metal-organic hybrid glasses with remarkable potential for the color-tunable afterglow. Therefore, this work not only provides a new horizon for modulating crystal and glass states with color/lifetime-tunable persistent luminescence, but also contributes to optical information storage and anti-counterfeiting technology.

The slow Arrhenius process in small organic molecules.

Equilibration, the complex set of molecular rearrangements leading to more stable states, is usually dominated by density fluctuations, occurring through the structural (α-)relaxation, whose timescale quickly increases upon cooling. Growing evidence shows, however, that equilibration can be reached also through an alternative pathway provided by the Slow Arrhenius process (SAP), a molecular mode slower than the structural processes in the liquid state and faster in glass. The SAP, widely observed in polymers, has not yet been reported in small molecules, probably because of the larger experimental difficulties in handling these systems. Here, we report the presence of the SAP in three different molecular glassformers, by investigating these systems in the thin film geometry via dielectric spectroscopy. These results reinforce the idea that the SAP is a universal feature of liquid and glassy dynamics.

Interparticle interaction-dependent jamming in colloids: insights into glass transition and morphology modulation during rapid evaporation-induced assembly.

Understanding the role of interparticle interactions in jamming phenomena is essential for gaining insights into the intriguing glass transition behavior observed in atomic and molecular systems. In this study, we investigate the jamming behavior of colloids with tunable interparticle interactions during evaporation-induced assembly (EIA). By manipulating the interaction among charged colloids using cationic polyethyleneimine (PEI) through electro-sorption and subsequent free polymer induced repulsion, we observe distinct jamming behavior in silica colloids during EIA, depending on the interparticle interactions. Silica colloids with strong repulsive interactions exhibit a repulsive colloidal glass state with a volume fraction of silica colloids in supraparticle ϕ ∼ 0.70. On the other hand, PEI-mediated attractive interactions among silica colloids lead to an attractive colloidal glass phase with a significantly lower ϕ ∼ 0.43. Free polymer induced repulsion of colloids at higher PEI concentration once again results in a repulsive glassy state with ϕ ∼ 0.61. Furthermore, we revealed that interparticle interactions not only influence the jamming behavior but also play a significant role in shaping the morphology of self-assembled structures during EIA, and the assembled structure undergoes a morphological reentrant transition from a doughnut-like shape to a spherical form and again back to a doughnut-like configuration. Jamming-dependent evolution of micropores and dynamics of the confined PEI have been probed using positron annihilation lifetime spectroscopy (PALS) and broadband dielectric spectroscopy (BDS). PALS reveals distinct variations in the micropores of the supraparticles with different PEI loadings, confirming the impact of jamming on the evolution of the micropores within the supraparticles. BDS measurements uncover non-monotonic dynamics of PEI molecules confined in the evolved pore network. It is revealed that the reentrant jamming behavior of colloids, modulated by PEI, holds profound significance for the long-term stability of supraparticles.

Aqueous Laponite® dispersions are attractive gels, not repulsive Wigner glasses: A critical commentary

An aqueous dispersion of Laponite® has been studied in the literature for over the past three decades. Typically, the aqueous dispersion of Laponite® undergoes incessant evolution of its microstructure, wherein its elastic modulus and the mean relaxation time show a continuous increase as a function of time. A considerable amount of discussion has revolved around the nature of this dispersion, specifically whether it can be classified as a repulsive Wigner glass state, characterized by disconnected Laponite® particles stabilized by electrostatic repulsions, or an attractive gel state, in which the particles form a percolated space-spanning network. The proponents of the Wigner glass state also conjecture that this system experiences a glass–glass transition after a period of 2 days has elapsed since its preparation. In this Commentary, we explore this topic from a rheological point of view, analyzing the published literature and performing new experiments. Aided by additional evidence from the literature, we propose that rheological behavior overwhelmingly suggests that an aqueous dispersion of Laponite® undergoes a sol–attractive gel transition and remains in the attractive gel state over at least up to 7 days without undergoing any additional transition. Importantly, rheology, despite being a macroscopic tool governed by principles of mechanics, offers profound insight into the microstructure of this particular system. The corresponding analysis conclusively determines the state of an aqueous dispersion of Laponite® to be an attractive gel.

Epitaxial strain manipulation of the cluster glass state in LaMnO3 films.

As a new-type magnetic state, the cluster glass state in manganite is arousing considerable attention due to its important theoretical value and extensive application prospects in condensed matter physics and spintronics. Due to the complex magnetic interactions, the cluster glass state is difficult to form and regulate in single films. Studies report a new phenomenon that epitaxial strain can regulate the formation of the cluster glass state in LaMnO3 (LMO) films. Comparing LMO thin films with different thicknesses grown on a (001)-oriented LaAlO3 (LAO) single crystal substrate, we found that the 20-nm-thick LMO film is more likely to form the cluster glass state than the 60-nm-thick and 120-nm-thick films. This can be attributed to the uneven distribution of strain and Mn ions in the depth profile. Our work demonstrates that thickness is an important method for regulating the formation of the cluster glass state in LMO films.

Rare coexistence of disorder-induced Griffiths phase and reentrant spin-glass state in a Heusler alloy Rh2FeAl with high Curie temperature

In this work, we report the synthesis of a Heusler alloy Rh2FeAl with valence electron count (VEC) 29 forming in B2-type structural disorder, where Fe atoms are distributed randomly with Al atoms between 4a and 4b Wyckoff positions (space group Fm3¯m, No: 225). Despite the structural disorder among the moment carrying Fe atoms, the compound exhibits ferromagnetic Curie temperature around TC ∼ 497 K. Nevertheless, the observation of Griffiths-phase (GP) like behaviour at TG ∼ 592 K suggests that atomic disorders brought down the bulk TC by about 95 K. The structural disorder also affects the ordered spin arrangements below TC through the development of a reentrant spin glass (RSG) state at low temperature. Both the GP like behaviour as well as RSG states are rarely observed in Heusler alloys while their coexistence is even rarer. The isothermal magnetisation as well as temperature dependence of resistivity behaviour ruled out the possibility of having half-metallic ferromagnetic characteristic in this material.

Enthalpy of anelasticity and rejuvenation of metallic glasses

Elastostatic loading and cryogenic thermal cycling are known to be capable of increasing the enthalpy of metallic glasses and improving their mechanical properties, effects of particular interest as these treatments operate in the nominally elastic regime. The increases in volume and stored energy induced by these treatments are studied for two prototypical (Pd- and Zr-based) bulk metallic glasses. The energy increase induced by elastostatic loading is associated with unrecovered anelastic strain, and not with viscoplastic strain as previously proposed. This energy increase decays similarly to that induced by thermal cycling, implying a storage mechanism that is similar for these two treatments and distinct from that operating under plastic deformation. For different as-cast and annealed states of metallic glasses, increased energy shows a linear correlation with increased volume. Property changes induced by elastostatic loading and thermal cycling also show a linear correlation, but with a different gradient, indicating greater excess volume for a given energy. It is proposed that the changes induced by treatments within the elastic limit do not constitute ‘rejuvenation’ of a metallic glass, but rather structural excitation localized at shear-transformation zones. The energetics of such excitation are analysed.

Fe doping induced cluster/spin glass state and metamagnetic transition in phase separated La0.5Sr0.5Mn1−xFexO3

We report the impurity doping effects in manganites La0.5Sr0.5Mn1−xFexO3 (0 ≤ x ≤ 0.2) and the field-induced metamagnetic transition in which the antiferromagnetic insulating phase transforms into ferromagnetic metallic phase. The Rietveld refined results of XRD data display no obvious structure change with a significant degree of Fe3+ doping on Mn sites. Significant ferromagnetism suppression and magnetic inhomogeneity tendency upon Fe3+-doping are evidenced, phase separated and spin-glass like states are identified. With applying a pulsed high magnetic field up to 50 T, a metamagnetic transition was induced, especially clear for x ≥ 0.1 compounds, which exhibited an irreversible phase transition from antiferromagnetic to ferromagnetic phase, and a saturation magnetization was obtained. The replacement of Mn3+ by Fe3+ ions eliminates the effects of lattice structure change on the magnetic and electronic properties because of the very similar ionic size of Mn3+ and Fe3+, but reduces the Mn3+/Mn4+ ratio and depopulates the number of available hopping sites and the hopping electrons, thus weakens the double exchange interaction. The occurrence of the AFM superexchange interaction via Fe3+–O2−–Fe3+ and Fe3+–O2−–Mn3+ bonds may bring about the competition between the antiferromagnetic ordering and the ferromagnetic ordering, leading to a cluster/spin-glass behavior in the samples with high Fe dopants concentration.

High-Temperature Ferroic Glassy States in SrTiO_{3}-Based Thin Films.

Disordered ferroics hold great promise for next-generation magnetoelectric devices because their lack of symmetry constraints implies negligible hysteresis with low energy costs. However, the transition temperature and the magnitude of polarization and magnetization are still too low to meet application requirements. Here, taking the prototype perovskite of SrTiO_{3} as an instance, we realize a coexisting spin and dipole reentrant glass states in SrTiO_{3} homoepitaxial films via manipulation of local symmetry. Room-temperature saturation magnetization and spontaneous polarization reach ∼ 10 emu/cm^{3} and ∼ 25 μC/cm^{2}, respectively, with high transition temperatures (101K and 236K for spin and dipole glass temperatures and 556K and 1100K for Curie temperatures, respectively). Our atomic-scale investigation points out an underlying mechanism, where the Ti/O-defective unit cells break the local translational and orbital symmetry to drive the formation of unusual slush states. This study advances our understanding of the nature of the intricate couplings of ferroic glasses. Our approach could be applied to numerous perovskite oxides for the simultaneous control of the local magnetic and polar orderings and for the exploration of the underlying physics.

Structural changes in a metallic glass under cyclic indentation

Using molecular dynamics simulation, a CuZr metallic glass was subjected to cyclic indentation to investigate cyclic hardening. Structural changes occurring after each indentation cycle were analyzed by examining the radial changes of the structural motifs in the vicinity of the indenter surface. The analysis revealed initial local structural modifications that corresponded to a more relaxed glass state, followed by a slow restoration of the initially destroyed structures. These findings provide new insights into the microstructural causes of cyclic hardening in metallic glasses.

Machine learning studies for liquid crystal texture recognition

ABSTRACT Machine learning techniques such as local binary pattern algorithm and convolutional neural network were applied to study textures of liquid crystal compound (S)-4’-(1-methyloctyloxycarbonyl) biphenyl-4-yl 4-[7-(2,2,3,3,4,4,4-heptafluorobutoxy) heptyl-1-oxy]-benzoate (3F7HPhH7). This compound exhibits in its polymorphism several smectic phases (smectic A, ferroelectric smectic C and antiferroelectric smectic C) and two glass states of antiferroelectric smectic C phase, which textures are difficult to distinguish. Proof-of-concept evidence is provided, demonstrating the ability of machine learning algorithms to identify transition temperatures and the respective phases involved. The article describes the procedure for preparing a dataset of textures obtained from polarised microscopy for classification using convolutional neural networks, especially in cases where the image dataset is unbalanced. It utilises the feature of their self-similarity and image augmentation, particularly the cropping procedure. A Kolmogorov–Smirnov test was conducted to check if selected images do not carry the same information.

Heterogeneous-elasticity theory of instantaneous normal modes in liquids

Since decades, the concept of vibrational density of states in glasses has been mirrored in liquids by the instantaneous-normal-mode spectrum. In glasses instantaneous configurations are believed to be situated close to minima of the potential-energy hypersurface and all eigenvalues of the associated Hessian matrix are positive. In liquids this is no longer true, and modes corresponding to both positive and negative eigenvalues exist. The instantaneous-normal-mode spectrum has been numerically investigated in the past, and it has been demonstrated to bring important information on the liquid dynamics and transport properties. A systematic deeper theoretical understanding is now needed. Heterogeneous-elasticity theory has proven to be particularly successful in explaining many details of the low-frequency excitations in glasses, ranging from the thoroughly studied boson peak, to other anomalies related to the crossover between wave-like and random-matrix-like excitations. Here we present an extension of heterogeneous-elasticity theory to the liquid state, and show that the outcome of the theory agrees well to the results of extensive molecular-dynamics simulations of a model liquid at different temperatures. We find that the spectrum of eigenvalues ρ(λ)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rho (\\lambda )$$\\end{document} has a sharp maximum close to (but not at) λ=0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\lambda =0$$\\end{document}, and decreases monotonically with |λ|\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$|\\lambda |$$\\end{document} on both its stable and unstable side. We show that the spectral shape strongly depends on temperature, being symmetric at high temperatures and becoming rather asymmetric at low temperatures, close to the dynamical critical temperature. Most importantly, we demonstrate that the theory naturally reproduces a surprising phenomenon, a zero-energy spectral singularity with a cusp-like character developing in the vibrational spectra upon cooling. This feature, known from a few previous numerical studies, has been generally overlooked in the past due to a misleading representation of the data. We provide a thorough analysis of this issue, based on both very accurate predictions of our theory, and computational studies of model liquid systems with extended size.